PhreeqcUsers Discussion Forum

Processes => Inverse modelling => Topic started by: Scarlet on January 18, 2018, 11:02:27 PM

Title: Phase mole transfers
Post by: Scarlet on January 18, 2018, 11:02:27 PM
Hi David,
when I enter these results I find that " Phase mole transfers"  is zero,I do not know why

Input

SOLUTION 1
    temp      25
    pH        7
    pe        4
    redox     pe
    units     mmol/kgw
    density   1
    -water    1 # kg



SOLUTION 2
    temp      25
    pH        9
    pe        4
    redox     pe
    units     mmol/kgw
    density   1
    C(4)      16
    Ca        8.3
    -water    1 # kg
INVERSE_MODELING 1
    -solutions      1        2
    -uncertainty    1        0.1
    -phases
        CO2(g)
        Calcite
    -balances
        C(4)        1        0.1
        Ca          1        0.1
        H(0)        1        0.1
    -tolerance         1e-10
    -uncertainty_water 1
    -mineral_water     true
END

output

Solution fractions:                   Minimum        Maximum
   Solution   1      9.821e-01      0.000e+00      0.000e+00
   Solution   2      1.000e+00      0.000e+00      0.000e+00

Phase mole transfers:                 Minimum        Maximum
         CO2(g)      7.263e-03      0.000e+00      0.000e+00   CO2
        Calcite      8.737e-03      0.000e+00      0.000e+00   CaCO3



Title: Re: Phase mole transfers
Post by: dlparkhurst on January 18, 2018, 11:35:48 PM
The mole transfer is the first number the two zeros that follow are related to the "range" calculation. If you include -range in the INVERSE_MODELING definition, then the minimum and maximum mole transfers are calculated that are consistent with the uncertainties that are assigned. See the manual or the WRR report for more information.
Title: Re: Phase mole transfers
Post by: Scarlet on January 29, 2018, 10:16:10 AM
thank you mr david, please I have 2 questions:
1-    can I know what is the difference between solution and solution spread?
2-    what is the role of uncertainty in the inverse modeling?
Title: Re: Phase mole transfers
Post by: dlparkhurst on January 29, 2018, 03:20:02 PM
SOLUTION_SPREAD is a spreadsheet-like input for solution data. It is equivalent to SOLUTION, but allows cutting and pasting from a spreadsheet to simplify data input.

You could read the manual or the WRR paper, but uncertainty defines the amount that input concentrations can be adjusted, so it is an estimate of your confidence in the analytical data. The charge imbalances of the solutions are a guide; the uncertainties must be at least large enough to account for the charge imbalance.
Title: Re: Phase mole transfers
Post by: Scarlet on January 31, 2018, 10:06:35 AM
thank you very much for your answer.
after execution of the program I had these results.
my question is: what can I rely on for an interpretation?
 Solution fractions:                   Minimum        Maximum
   Solution   1      1.001e+00      0.000e+00      0.000e+00
   Solution   2      1.000e+00      0.000e+00      0.000e+00

Phase mole transfers:                 Minimum        Maximum
        Calcite     -7.895e-03      0.000e+00      0.000e+00   CaCO3
       Dolomite      7.895e-03      0.000e+00      0.000e+00   CaMg(CO3)2
         CO2(g)     -7.895e-03      0.000e+00      0.000e+00   CO2
         Pyrite      7.368e-03      0.000e+00      0.000e+00   FeS2
          O2(g)      2.763e-02      0.000e+00      0.000e+00   O2
         Albite      7.138e-02      0.000e+00      0.000e+00   NaAlSi3O8
         Quartz     -1.429e-01      0.000e+00      0.000e+00   SiO2
      Kaolinite     -3.564e-02      0.000e+00      0.000e+00   Al2Si2O5(OH)4
         Halite      7.823e-02      0.000e+00      0.000e+00   NaCl
     Fe(OH)3(a)     -7.227e-03      0.000e+00      0.000e+00   Fe(OH)3

Redox mole transfers:   
          Fe(3)     -7.367e-03
           O(0)      5.526e-02
          S(-2)      1.474e-02

Sum of residuals (epsilons in documentation):         6.012e+00
Sum of delta/uncertainty limit:                       6.011e+00
Maximum fractional error in element concentration:    1.000e+00
Title: Re: Phase mole transfers
Post by: dlparkhurst on January 31, 2018, 03:43:45 PM
First, look at your saturation indices.

The mole transfers of silicates is larger than carbonates. Does that make sense? Consider the net effect of the carbonate reactions.
Title: Re: Phase mole transfers
Post by: Scarlet on February 07, 2018, 11:25:39 AM
I can know by what method can I represent the results? graph  or board?

and why we have several results of phase mole transfers and redox mole transfers?

thank you very much
Title: Re: Phase mole transfers
Post by: dlparkhurst on February 07, 2018, 05:16:46 PM
You are on your own to present results.

Mole balance modeling frequently does not give a unique result. Several sets of phases can account for the changes in water composition.
Title: Re: Phase mole transfers
Post by: Scarlet on February 14, 2018, 03:59:15 PM
Hi David,
please can I do the inverse modeling of these two solutions?
 because after execution I find 216 models. Is that right?

SOLUTION 1
    temp      25
    pH        7
    pe        4
    redox     pe
    units     ppm
    density   1
    Ca        21
    Cl        9
    K         0.8
    N(5)      1.6
    Na        1.6
    S(6)      9.5
    -water    1 # kg
SOLUTION 2
    temp      25
    pH        8.32
    pe        4
    redox     pe
    units     ppm
    density   1
    Al        2.499
    As        97.05
    B         2461
    Ba        76.8
    Ca        0
    Cl        2703
    Cs        3.3
    Fe        7.661
    K         118.37
    Li        1160
    Mg        187.07
    Mn        8.253
    N(5)      0
    Na        3427.51
    Pb        0.021
    S         1379.59
    U         276.4
Title: Re: Phase mole transfers
Post by: dlparkhurst on February 14, 2018, 04:46:17 PM
The number of models depends most on the number of phases and the constraints on the phases. More phases allows more models, and more constraints decrease the number of models.

As for your waters, I suggest you ignore the elements that are not in large concentrations in either the phases or the water. Inverse modeling requires the stoichiometry of the minerals, which may not be well defined for trace elements. So work on the major element (including all major elements in the solution and phases) reactions.
Title: Re: Phase mole transfers
Post by: Scarlet on February 15, 2018, 03:04:47 PM
thank you very much Mr david.
after eliminating oligo element, I found 12 models.
I want to represent the models on graphs but I do not know what to choose as elements to better represent my results.
Can you help me please?